If you've ever stayed up the whole night through, you may have noticed that you begin to feel cold in the hours just before morning. Why does this happen?
It's not just humans that know how to groove. Other mammals do too!
Pacemakers are electrical devices that monitor the heart rate and helps get it up to speed when it starts pumping too slowly. The small battery powered disk is inserted just beneath the skin above the heart. A couple of attached wires monitor the heart and carry signals and impulses to and from the heart.